In an electronic card that, on a printed circuit, includes both a microprocessor and memories meant to contain confidential information that is not to be accessible to a defrauder, access to these memories must be protected by physical means. Such access protection by physical means can be circumvented, however, by means that destroy the protection without damaging the memories or their contents. This means that the use of these destructive means must be prevented as completely as possible. Likewise, if the ambient temperature has been lowered far enough before a memory is disconnected from its power supply system, the memory will save the contents even after the power cutoff.